Using JSON in Google Flights

I need to make an application that uses JSON array to send and receive data from the RPC server. It is an application that searches for air fares. The idea is that in the field, enter the starting point and destination and travel dates, etc. This information is required to send as JSON object/array to RPC server that returns JSON field again.
it's about Google's RPC server that requires HTTP POST request.

The link below is an example JSON fields that server back, but I do not know how to generate JSON array:

JSONParser class do the staff: execute http POST request based on given JSON data, etc.
error I get is as follows:
"Error parsing data org.json.JSONException: Value <!DOCTYPE of type java.lang.String cannot be converted to JSONObject"

My English is not very good, so I apologize to the possible grammatical errors in the text.